Steam turbines are each equipped with a turbine main body having a rotor that is used for mechanical drive and is rotatably supported. Steam acting as a working fluid is supplied to the turbine main body, and thereby the rotor is rotatably driven. In the steam turbine, the steam supplied to the turbine main body or steam extracted from the turbine main body flows in a steam channel. The steam channel is provided with a regulating valve, and the regulating valve adjusts opening/closing of the steam channel, thereby regulating a flow rate of steam. To drive the regulating valve, a hydraulic servomechanism is widely used (e.g., see Patent Literature 1).
Here, FIG. 11 is a schematic view showing a configuration of a conventional steam turbine 80. The steam turbine 80 includes a turbine main body 81 driving a compressor, a steam channel 82 supplying steam to the turbine main body 81, a regulating valve 83 that is provided for the steam channel 82 and adjusts opening/closing of the steam channel 82, a lever member 84 which is rotatably supported and to which one end of the regulating valve 83 is fixed, a hydraulic servomechanism 85 driving the regulating valve 83 via the lever member 84, and an electronic governor 86 controlling an operation of the hydraulic servomechanism 85 based on a rotation speed detected from the turbine main body 81 and an instruction input from a control panel.
Here, the hydraulic servomechanism 85 has, as shown in FIG. 11, a piston 87, one end of which is fixed to the lever member 84, a hydraulic cylinder 88 housing the piston 87, a pilot valve 89 supplying hydraulic oil to the hydraulic cylinder 88, and an actuator 90 driving the pilot valve 89. According to the hydraulic servomechanism 85 configured in this way, when the hydraulic oil is supplied from the pilot valve 89 below the piston 87 in the hydraulic cylinder 88, the piston 87 moves upward, and thereby the lever member 84 is rotated to force a tip thereof to move up. Thereby, the regulating valve 83 fixed to the lever member 84 also moves up, and the steam channel 82 is opened. Thereby, the steam is supplied from the steam channel 82 to the turbine main body 81.
In contrast, when the hydraulic oil is supplied from the pilot valve 89 above the piston 87 in the hydraulic cylinder 88, the piston 87 moves downward, and thereby the lever member 84 is rotated to force the tip thereof to move down. Thereby, the regulating valve 83 fixed to the lever member 84 also moves down, and the steam channel 82 is closed. Thereby, the supply of the steam from the steam channel 82 to the turbine main body 81 comes to a stop.
Here, FIG. 12 is a schematic perspective view showing an installed state of a conventional hydraulic servomechanism 85. Typically, a facility installing space inside a facility building is for the most part occupied by a machine to be driven and a turbine main body. The hydraulic servomechanism 85 requires a space in a downward direction of the lever member 84 because the lever member 84 is operated up and down. However, as described above, since most of the installing space is occupied by the machine to be driven and the turbine main body, it is difficult for only the hydraulic servomechanism 85 to occupy the space below the lever member 84. For this reason, the piston 87 and the hydraulic cylinder 88 directly operating the lever member 84 are disposed directly under the lever member 84, whereas the pilot valve 89 and actuator 90 are installed on the bearing cover 91, thereby securing the installing space. The bearing cover 91 houses a bearing that functions to rotatably support a rotating shaft constituting the rotor of the turbine main body 81.